Breathing gas mask



FIG. 1 shows a side elevation view of my ornamental design for a breathing gas mask;

FIG. 2 shows a front elevation view of the mask;

FIG. 3 shows a rear view looking inwardly toward the mask in the direction of lines 3--3 of FIG. 1;

FIG. 4 shows a midline sectional view through the mask in the direction of lines 4--4 of FIG. 2;

FIG. 5 shows a view looking downwardly from the top of the mask; and,

FIG. 6 shows a view looking upwardly at the bottom of the mask. 

The ornamental design for a breathing gas mask, as substantially shown. 